I have 3 programs that I had setup using g76 and it always ends up over size . I end up adjusting wear offset in X -.011 approx. to get gage to fit or get PD correct.
I am using the minor diameter from machinery hand book and using K value difference between major and minor/2. Spring passes shallow depth etc. I am using walter inserts with sharp point.
On a repeat job I had to fudge the Minor diameter by .012 and it always comes out correct with little or no wear adjustment. 1.50-12 thread.
N6 T404 (THD TOOL)
(1.50 X.12)
( USE GAGE TO CHECK )
( WALTER THREADING INSERT )
( NTS-ER -16 AG60 WXP20)
G50 S1250
G97 S500 M03
G54 G00 X2.1 Z1. M08
G96 S400
G00 X1.6 Z0.1
M24
(PD = 1.4008)
(PD ADJUSTMENT FOR INSERT =.047/2)
(K= NEW PD FOR INSERT)
G76 X1.3773 (X1.4008) Z-1.2 K0.0614 (K.0496) F0.083 D0.003
G00 X2.1
G97 S500 M09
Z1.
G28
M01